The present invention relates to a new reed switch construction, and more particularly to a novel glass envelope for use in such construction.
A reed switch is a magnetically controlled switch that automatically makes, breaks, or holds contact in an electrical circuit. Such switches are widely used for electrical circuit control, particularly in the communications field.
The conventional form of dry reed switch includes two magnetic metal reeds which have overlapping, flat, end portions separated by a small gap when the switch is open. The reeds are hermetically sealed in opposite ends of a tubular glass envelope filled with an inert atmosphere. When a magnetic field is applied to such a switch, the flat, overlapping portions of the reeds are attracted to each other, thus closing the switch and conducting an electric current. The reeds are caused to separate, thus opening the circuit, upon removal of the magnetic field. Good electrical contact is assured by plating a thin layer of precious metal over the flat contact portions of the reeds.
In production, a metal reed is inserted in each end of a glass tube and the end of the tube thermally softened to collapse about and seal to a shank portion on the reed. This sealing operation has been greatly facilitated by drawing the tubular enclosure from an infrared absorbing glass, and using an infrared heat source to concentrate heat in a small sealing zone on the glass tube.